Anti-melanogenesis and anti-tyrosinase properties of aryl-substituted acetamides of phenoxy methyl triazole conjugated with thiosemicarbazide: Design, synthesis and biological evaluations.

A series of aryl phenoxy methyl triazole conjugated with thiosemicarbazides were designed, synthesized, and evaluated for their tyrosinase inhibitory activities in the presence of l-dopa and l-tyrosine as substrates. All the compounds showed tyrosinase inhibition in the sub-micromolar concentration. Among the derivatives, compound 9j bearing benzyl displayed exceptionally high potency against tyrosinase with IC50 value of 0.11 µM and 0.17 µM in the presence of l-tyrosine and l-dopa as substrates which is significantly lower than that of kojic acid as the positive control with an IC50 value of 9.28 µM for l-tyrosine and 9.30 µM for l-dopa. According to Lineweaver-Burk plot, 9j demonstrated an uncompetitive type of inhibition in the kinetic assay. Also, in vitro antioxidant activities determined by DPPH assay recorded an IC50 value of 68.43 µM for 9i. The melanin content of 9j was determined on B16F10 melanoma human cells which demonstrated a significant reduction of the melanin content. Moreover, the binding energies corresponding to the same ligand as well as computer-aided drug-likeness and pharmacokinetic studies were also carried out. Compound 9j also possessed metal chelation potential correlated to its high anti-TYR activity.

Comparison Study of the Effects of Cationic Liposomes on Delivery across 3D Skin Tissue and Whitening Effects in Pigmented 3D Skin.

Charged phospholipids are employed to formulate liposomes with different surface charges to enhance the permeation of active ingredients through epidermal layers. Although 3D skin tissue is widely employed as an alternative to permeation studies using animal skin, only a small number of studies have compared the difference between these skin models. Liposomal delivery strategies are investigated herein, through 3D skin tissue based on their surface charges. Cationic, anionic, and neutral liposomes are formulated and their size, zeta-potential, and morphology are characterized using dynamic light scattering and cryogenic-transmission electron microscopy (cryo-TEM). A Franz diffusion cell is employed to determine the delivery efficiency of various liposomes, where all liposomes do not exhibit any recognizable difference of permeation through the synthetic membrane. When the fluorescence liposomes are applied to 3D skin, considerable fluorescence intensity is observed at the stratum cornea and epithelium layers. Compared to other liposomes, cationic liposomes exhibit the highest fluorescence intensity, suggesting the enhanced permeation of liposomes through the 3D skin layers. Finally, the ability of niacinamide (NA)-incorporated liposomes to suppress melanin transfer in pigmented 3D skin is examined, where cationic liposomes exhibit the highest degree of whitening effects.

Fabrication, characterization and comparison of α-arbutin loaded dissolving and hydrogel forming microneedles.

In this study, polyacrylic acid-co-maleic acid (PAMA) and polyvinyl alcohol (PVA) (1:4) were used to fabricate dissolving microneedles (DMNs) and hydrogel forming microneedles (HMNs) which incorporated α-arbutin. Αlpha-arbutin is commonly used as a skin lightening agent. However, it has poor penetration ability due to its hydrophilic properties. The purpose of this study was to compare the permeation of α-arbutin into the skin using DMNs and HMNs. Both types of microneedles (MNs) were sharp, strong with elegant appearance and approximately 100% penetrated the neonatal porcine skin. All needles of α-arbutin loaded DMNs were completely dissolved within 45 min, whereas maximum swelling of HMNs was observed at 4 h. In vitro permeation studies showed that α-arbutin loaded DMNs and HMNs provided significantly about 4.5 and 2.8 times, respectively, greater α-arbutin permeability than gel and commercial cream (P < 0.05). In vivo study also showed high intradermal delivery of α-arbutin levels using DMNs (5.33 µg/mL) and HMNs (1.47 µg/mL) when compared to that of commercial cream 0.15 µg/mL. Moreover, the micro-holes caused by applying MNs can reseal within 1 h. MNs were also stable at 25 °C for 3 months. The results suggested that DMNs and HMNs developed have a promising platform for transdermal delivery.

Hybrid polymeric microspheres for enhancing the encapsulation of phenylethyl resorcinol.

Phenylethyl resorcinol (PR) has been known to allow the whitening effect by inhibiting formation of tyrosinase. PR has solubility of 4.05 ± 0.02 mg/g for water and log P of 3.017, proposed an amphiphilic substance. Hybrid PLGA microspheres with oil (HPMSs) have been used to improve encapsulation efficiency (EE) of hydrophilic molecules and control the release of them. The solubility (618.3 ± 22.29 mg/g) of PR was the highest in CapryolTM 90. The formulations (F6 and F`6) were selected after evaluation with EE and the released % (w/w) at 8 h. HPMSs showed 40% (w/w) increase of EE compared to that in CPMSs. Retention study on rat skin at 12 h resulted in that PR of HPMSs was remained more than that of CPMSs in dermal layer forming the melanin. HPMSs showed 1.4-fold increase of tyrosinase inhibition significantly in melanoma cells than that of the PR solution at 24 h.

The clinical effect of glutathione on skin color and other related skin conditions: A systematic review.

BACKGROUND: Glutathione is one of agents which is commonly used to lighten skin color in Asia as a dietary supplement. Previous studies suggest its potential effect of glutathione on skin color. However, the clinical efficacy of glutathione in oral form is still questionable due to its limited absorption and bioavailability. AIM: To determine the clinical effects of glutathione on skin color and related skin conditions. PATIENTS/METHODS: A systematic review was conducted using PubMed, CINAHL, Scopus, EMBASE and Cochrane library were searched from inceptions to October 2017. All clinical studies evaluating the effect of glutathione on any skin effects in healthy volunteer were included. RESULTS: A total of four studies were included. Three studies were RCTs with placebo control, while one was a single-arm trial. One study used topical form, while others used oral form of glutathione with 250 to 500 mg/day. We found that both oral glutathione with the dosage of 500 mg/day and topical 2.0% oxidized glutathione could brighten skin color in sun-exposed area measured by skin melanin index. No significant differences in the reduction in skin melanin index were observed in sun-protected area for any products. In addition, glutathione also has a trend to improve skin wrinkle, skin elasticity, and UV spots. Some adverse events but nonserious were reported. CONCLUSIONS: Current evidence of the skin whitening effect of glutathione is still inconclusive due to the quality of included studies and inconsistent findings. However, there is a trend that glutathione might brighten skin color at skin-exposed area.

Clinical evaluation of the lightening effect of cytidine on hyperpigmented skin.

BACKGROUND: Melanocytes, which reside in the basal layer of the epidermis, produce the pigment melanin in cytoplasmic organelles known as melanosomes. Melanosomes are transferred to keratinocytes which provide the color in our skin. Recently, Diwakar et  al reported the crucial roles of protein glycosylation in both melanogenesis and melanosome transfer to keratinocytes, and each was inhibited by the nucleotide cytidine. OBJECTIVE: The main objective of this study was to determine the clinical effects of topical application of cytidine to the hyperpigmented regions of the face in a group of human volunteers. METHODS: A randomized, vehicle-controlled study was conducted for 12 weeks on healthy Korean female subjects. Cytidine was formulated into the lotion at concentrations of 2%, 3%, and 4% (w/w) and compared to the vehicle control formulation. The clinical outcomes were evaluated by performing visual assessment grading, measuring melanin index, skin brightness, and skin color parameters. In vitro skin penetration studies were conducted using Franz cell chambers for the 2% cytidine test formulation. RESULTS: The test group showed significant improvements in the visual assessment scores, melanin index, skin brightness, and skin color compared to the control group. Although significant dose-dependent improvements were seen in the clinical study, the in vitro Franz cell studies indicated that the clinical efficacy and potency of cytidine might be further enhanced by formulating a better topical delivery system, which will be the goal of our future studies. CONCLUSIONS: This randomized, double-blind, 12-week clinical study successfully demonstrated the efficacy of cytidine on skin depigmentation in a dose-dependent manner.

Biochemical Mechanism of Rhododendrol-Induced Leukoderma.

RS-4-(4-hydroxyphenyl)-2-butanol (rhododendrol (RD))-a skin-whitening ingredient-was reported to induce leukoderma in some consumers. We have examined the biochemical basis of the RD-induced leukoderma by elucidating the metabolic fate of RD in the course of tyrosinase-catalyzed oxidation. We found that the oxidation of racemic RD by mushroom tyrosinase rapidly produces RD-quinone, which gives rise to secondary quinone products. Subsequently, we confirmed that human tyrosinase is able to oxidize both enantiomers of RD. We then showed that B16 cells exposed to RD produce high levels of RD-pheomelanin and protein-SH adducts of RD-quinone. Our recent studies showed that RD-eumelanin-an oxidation product of RD-exhibits a potent pro-oxidant activity that is enhanced by ultraviolet-A radiation. In this review, we summarize our biochemical findings on the tyrosinase-dependent metabolism of RD and related studies by other research groups. The results suggest two major mechanisms of cytotoxicity to melanocytes. One is the cytotoxicity of RD-quinone through binding with sulfhydryl proteins that leads to the inactivation of sulfhydryl enzymes and protein denaturation that leads to endoplasmic reticulum stress. The other mechanism is the pro-oxidant activity of RD-derived melanins that leads to oxidative stress resulting from the depletion of antioxidants and the generation of reactive oxygen radicals.

Skin Pretreatment With Conventional Non-Fractional Ablative Lasers Promote the Transdermal Delivery of Tranexamic Acid.

BACKGROUND: Laser pretreatment of skin can be used to enable drugs used in dermatology to penetrate the skin to the depth necessary for their effect to take place. OBJECTIVE: To compare the permeation of tranexamic acid after conventional non-fractionated ablative Er:YAG and CO2 laser pretreatment in a laser-aided transdermal delivery system. MATERIALS AND METHODS: An erbium-doped yttrium aluminium garnet (Er:YAG) and a CO2 laser were used to pretreat dorsal porcine skin. Scanning electron microscopy was used to examine disruption of the skin surface. Confocal laser scanning microscopy was used to determine the depth of penetration of a reporter molecule (fluorescein isothiocyanate) into the skin. A Franz diffusion assembly was used to examine fluency-related increases in transdermal delivery of transexamic acid. RESULTS: Transdermal delivery of tranexamic acid increased as Er:YAG laser fluency increased. Transdermal delivery was higher when CO2 laser pretreatment was used than when Er:YAG laser pretreatment was used, but a "ceiling effect" was present and increasing the wattage did not cause a further increase in delivery. CO2 laser pretreatment also caused more extensive and deeper skin disruption than Er:YAG laser pretreatment. CONCLUSION: For conventional, non-fractionated ablative laser pretreatment, the Er:YAG laser would be an optimal choice to enhance transdermal penetration of transexamic acid.

In vitro Dermal Absorption of Hydroquinone: Protocol Validation and Applicability on Illegal Skin-Whitening Cosmetics.

In Europe, hydroquinone is a forbidden cosmetic ingredient. It is, however, still abundantly used because of its effective skin-whitening properties. The question arises as to whether the quantities of hydroquinone used become systemically available and may cause damage to human health. Dermal absorption studies can provide this information. In the EU, dermal absorption has to be assessed in vitro since the Cosmetic Regulation 1223/2009/EC forbids the use of animals. To obtain human-relevant data, a Franz diffusion cell protocol was validated using human skin. The results obtained were comparable to those from a multicentre validation study. The protocol was applied to hydroquinone and the dermal absorption ranged between 31 and 44%, which is within the range of published in vivo human values. This shows that a well-validated in vitro dermal absorption study using human skin provides relevant human data. The validated protocol was used to determine the dermal absorption of illegal skin-whitening cosmetics containing hydroquinone. All samples gave high dermal absorption values, rendering them all unsafe for human health. These results add to our knowledge of illegal cosmetics on the EU market, namely that they exhibit a negative toxicological profile and are likely to induce health problems.

Synthesis and Biological Evaluation of Resveratrol Derivatives as Melanogenesis Inhibitors.

Resveratrol (1), a naturally occurring stilbene compound, has been suggested as a potential whitening agent with strong inhibitory activity on melanin synthesis. However, the use of resveratrol in cosmetics has been limited due to its chemical instability and poor bioavailability. Therefore, resveratrol derivatives were prepared to improve bioavailability and anti-melanogenesis activity. Nine resveratrol derivatives including five alkyl ether derivatives with C2H5, C4H9, C5H11, C6H13, and C8H17 (2a-2e) and four ester derivatives with CH3, CH=C(CH3)2, CH(C2H5)C4H9, C7H15 (3a-3d) were newly synthesized and their effect on melanin synthesis were assessed. All the synthetic derivatives efficiently reduced the melanin content in α-MSH stimulated B16F10 melanoma cells. Further investigation showed that the inhibitory effect of 2a on melanin synthesis was achieved not by the inhibition of tyrosinase activity but by the inhibition of melanogenic enzyme expressions such as tyrosinase and tyrosinase-related protein (TRP)-1. Our synthetic resveratrol derivatives have more lipophilic properties than resveratrol by the addition of alkyl or acyl chains to free hydroxyl moiety of resveratrol; thus, they are expected to show better bioavailability in skin application. Therefore, we suggest that our synthetic resveratrol derivatives might be promising candidates for better practical application to skin-whitening cosmetics.